(Yicai Global) May 16 -- A Chinese survey ship has completed research and extraction at a natural combustible ice seep in the South China Sea, state-broadcaster CCTV said today.

The Ocean Six research vessel equipped with staff and devices from 18 research institutes arrived in Guangzhou today after the 36-day survey mission. The cold seep is between 1,200 and 1,400 meters deep. 

Researchers took samples and made detailed observations, said Chen Zongheng, a researcher at the Guangzhou Marine Geological Survey.

The expedition team also tested several self-developed equipment in the deep sea, including deep sea mining vehicles, deep-sea hydrothermal exploration submersibles, and several large gas hydrates monitors. The team collected expected data from the tests, said Chen Ming, a senior engineer of the Institute of Deep-Sea Science and Engineering at Chinese Academy of Science.

The seep was first discovered in 2000 and the country undertook trial mining there in 2017 for the first time. The energy density of combustible ice is two to five times that of natural gas, 10 times that of coal, and it emits little polluting gas after combustion.